An investigation of New York City’s Gowanus Canal has revealed the waterway’s widespread contamination, which authorities say poses a threat to people and the environment.

The Environmental Protection Agency on Wednesday released a study that assessed the pollution of the 1.5-mile canal, which was named eligible for the federal Superfund cleanup program last year.

The channel, which flows through an industrial area near affluent Brooklyn neighborhoods, is tainted with various metals and over a dozen contaminants, including suspected carcinogens like polychlorinated biphenyls (PCBs), the EPA said.

Under the Superfund program, the government will force polluters to pay for the canal’s cleanup. Officials say restoration will require major dredging and will last 10 to 11 years beginning in 2015 at a cost of $300 to $500 million.

The EPA said the canal also contains the contaminate polycylic aromatic hydrocarbons, or PAHs, another suspected carcinogen.

Agency regional administrator Judith A. Enck told the New York Times that people should refrain from swimming in the canal and eating fish from it.

“What we found is no surprise,” she said. “The report paints a pretty serious picture of the level of contamination.”

Mayor Michael Bloomberg has opposed Gowanus’ designation as a Superfund site, saying the label would scare off developers.